A conventional approach for a temperature measurement uses a voltage which increases linearly with temperature. This so-called PTAT (proportional-to-absolute-temperature) voltage is typically generated from the difference of two base-emitter voltages of PNP bipolar transistors, which are biased with different current densities (e.g. ratio 1:N).
An actual temperature value can be extracted by comparing the ptat voltage (=“dVbe”) to a temperature independent reference (e.g. a bandgap). In practice, this is achieved by measuring the ptat voltage (or a multiple of it) directly with an analog-to-digital-converter (ADC), which in turn includes (or is controlled by) such reference.
In general, a temperature measurement with a higher accuracy is desired.